Heat-treatment apparatus for synthetic fiber yarns

ABSTRACT

A heat-treatment apparatus for synthetic fiber yarns is described, in which one side wall of a vertically elongated sealed vessel is formed of a heat-exchanging wall, a small amount of liquid thermal medium is enclosed within said vessel, a vertically elongated heater is provided in said vessel with its lower end portion submerged in said liquid thermal medium, and an inclined guide plate is disposed between said heat-exchanging wall and said heater so that a return liquid thermal medium condensed on the heat-exchanging wall may be fed to the heater in a thin film form and heated thereby through its increased heating surface area to fill almost all the inner space of said vertically elongated vessel with a saturated vapor of said liquid thermal medium, and in which a separator tank communicated with the upper portion of said vertically elongated vessel is communicated through a return pipe to an inner portion just above said heater of said vertically elongated vessel so that the return liquid thermal medium condensed in the separator tank may be fed onto the heater in a thin film form.

Kodaira HEAT-TREATMENT APPARATUS FOR SYNTHETIC FIBER YARNS [76] Inventor: Nobuhisa Kodaira, 1-1-10 Shoan,

Suginami-ku, Tokyo, Japan [22] Filed: May 17, 1974 [21] Appl. No.: 470,915

[52] US. Cl. 219/326; 28/62; 57/34 HS; 165/32; 165/105; 219/272; 219/273; 219/388; 219/401; 219/530 [51] Int. Cl. 1105b 1/02 [58] Field of Search 219/271, 272, 273, 274, 219/275, 326, 388, 401, 439, 530, 540; 28/62; 57/34 HS; 165/32, 105; 34/155 [56] References Cited UNITED STATES PATENTS 2,547,865 4/1951 219/274 X 3,234,357 2/1966 Seuthe 219/273 3,395,433 8/1968 Kodaira et al. 28/62 3,396,524 8/1968 Parker 57/34 HS 3,431,396 3/1969 Kodaira 219/326 3,603,767 9/1971 Scicchitano 219/439 3,638,411 2/1972 Tsugawa et a1. 57/34 HS 3,719,795 3/1973 Bolomier et a1. 219/272 3,728,518 4/1973 Kodaira 219/326 3,770,051 11/1973 Kodaira 165/105 3,823,307 7/1974 Weiss 219/439 :1 2 I I i I I 5 r 4 g 1 Apr. 22, 1975 Primary Examiner-Volodymyr Y. Mayewsky Attorney, Agent, or Firm-Cullen, Settle, Sloman & Cantor [57] ABSTRACT A heat-treatment apparatus for synthetic fiber yarns is described, in which one side wall of a vertically elongated sealed vessel is formed of a heat-exchanging wall, a small amount of liquid thermal medium is enclosed within said vessel, a vertically elongated heater is provided in said vessel with its lower end portion submerged in said liquid thermal medium, and an inclined guide plate is disposed between said heatexchanging wall and said heater so that a return liquid thermal medium condensed on the heat-exchanging wall may be fed to the heater in a thin film form and heated thereby through its increased heating surface area to fill almost all the inner space of said vertically elongated vessel with a saturated vapor of said liquid thermal medium, and in which a separator tank communicated with the upper portion of said vertically elongated vessel is communicated through a return pipe to an inner portion just above said heater of said vertically elongated vessel so that the return liquid thermal medium condensed in the separator tank may be fed onto the heater in a thin film form.

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HEAT-TREATMENT APPARATUS FOR SYNTHETIC FIBER YARNS The present invention relates to improvements in a heat-treatment apparatus for synthetic fiber yarns such as, for example, a stretching machine, a pre-twisting machine, a stretching and pre-twisting machine, etc.

More particularly, the invention relates to a heattreatment appatus in which a small amount of liquid thermal medium is enclosed at the bottom of a vertically elongated vacuum-sealed vessel to heat a heatexchanging wall forming a part of said vacuum-sealed vessel with a saturated vapor of said liquid thermal medium which is generated upon heating said liquid thermal medium by means of a heater submerged therein, and thus the heat preserved by said thermal medium vapor is transferred to the yarns moving in contact with the outer surface of said heat-exchanging wall, whereby said yarns may be heat-treated.

For the above-mentioned type of heat-treatment apparatus, it is desired that said apparatus can withstand against a long period of use and it can continue operation even under repairs. In addition, in view of the na ture of the apparatus it is required to make the temperature distribution uniform over the entire length of the elongated heat-exchanging wall surface, and also to make the amount of the liquid thermal medium minimum for minimizing damages caused by possible accidents such as a fire of a plant building.

It is an object of the present invention to provide a novel heat-treatment apparatus in which a liquid thermal medium is heated in a thin film form by means of a heater to enlarge the effective heat transfer area from said heater for enhancing a rate of vaporization of said liquid thermal medium and also to prevent said liquid thermal medium from being degraded upon heating.

Another object of the present invention to provide a novel heat-treatment apparatus in which temperature distribution can be maintained uniform for a long period of time over the entire length of a vertically elongated sealed vessel.

Still another object of the present invention is to provide a novel heat-treatment apparatus in which upon extracting an impority gas from a sealed vessel, the extraction can be easily performed even if said apparatus is in use for heat-treatment.

Yet another object of the present invention is to provide a novel heat-treatment apparatus in which a less amount of liquid thermal medium is required than the case where conventional heating devices of the type of submerging a heater entirely in a thermal medium liquid is used.

According to one feature of the present invention, as the most preferable structure to achieve the aforementioned objects, there is provided a heat-treatment apparatus for synthetic fiber yarns; in which a part of a vertically elongated sealed vessel is formed of a heatexchanging wall, an electric heater covered with ahheat-resistive and porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium is provided in the lower half portion of the inner space of said vessel with its lower end portion submerged in said liquid thermal medium enclosed within said vessel, and a return guide plate is disposed between the inside surface of said heatexchanging wall and said electric heater exposed above the liquid thermal medium level; and in which a separator tank is provided in communication with the upper portion of said vertically elongated vessel, and the bottom of said separator tank is communicated through a return pipe with an inner portion just above said heater of the vertically elongated sealed vessel.

These and other objects and features of the present invention will be more fully understood from the following description taken with reference to the accompanying drawings, in which:

FIG. I is a front view of a heat-treatment apparatus for synthetic fiber yarns according to the present invention,

FIG. 2 is a longitudinal cross-section view taken along line IIII in FIG. 1,

FIG. 3 is a transverse cross-section view taken along line III-III in FIG. 2,

FIG. 4 is a transverse cross'section view taken along line IV-IV in FIG. 2,

FIG. 5 is an enlarged cross-section view of a part of the structure shown in FIG. 2,

FIG. 6 is an enlarged cross-section view of a part of a modified embodiment corresponding to the part shown in FIG. 5,

FIG. 7 is a partial longitudinal cross-section view of a part of the modified embodiment corresponding to a part of the apparatus shown in FIG. 2,

FIG. 8 is a transverse cross-section view of the modified embodiment corresponding to FIG. 4, and

FIG. 9 is a partial longitudinal cross-section view of a part of a further modified embodiment corresponding to the part shown in FIG. 7.

Referring now to FIGS. 1 to 5 of the drawings which illustrate one preferred embodiment of the present invention, reference numeral 1 designates a vertically elongated sealed vessel, and in a thermal medium vapor chamber formed within said vessel 1 is disposed a U- shaped electric heater 2 having its outer surface covered with a porous material 28 which has a heatresistivity and a porosity such that capillarity may occur therein for a given liquid thermal medium. Then the lower end portion of said heater 2 is submerged in a small amount of liquid thermal medium 3 which is enclosed within said vessel 1 and retained at its bottom portion, but the most part of the remainder of said heater 2 is exposed in said thermal medium vapor chamber. On the outside surface of a heat-exchanging wall 4 of the vessel 1 are formed vertically elongated grooves 5, while inside of the same are disposed return guide plates 6 at an inclined attitude, with its upper end contacting to said heat-exchanging wall 4 and its lower end terminating in the proximity of the outer surface of said electric heater 2 exposing above the level of the liquid thermal medium 3.

An electric power supply is connected to the electric heater 2 to raise its temperature, so that the liquid thermal medium 3, which then takes a thin film form within the porous material 28 outside of the heater 2, is heated and vaporized. The saturated vapor of the thermal medium then fills the inner space of the vertically elongated vessel 1 and thus heats the heat-exchanging wall 4 uniformly over its entire length. Yarns 7 moving along the grooves 5 are heat-treated with the heat preserved by the saturated vapor. Then the vapor is cooled and condensed into drops of return liquid thermal medium adhered onto the inner surface of the heatexchanging wall 4, which are led to the electric heater 2 along the inclined surface of the return guide plates 6. The return liquid thermal medium led to the electric heater 2 is heated thereby and again voporized, and the thermal medium vapor fills the inner space of the vessel 1. The above-described state is shown in detail in FIG. 5. In this figure, reference numeral 8 designates drops of return liquid thermal medium formed on the inside surface of the heat-exchanging wall 4, and numeral 9 designates a thin film of return liquid thermal medium formed when the drops of return liquid thermal medium 8 aggregate, which film is formed along the surface of the guide plate 6 up to the surface of the heater 2. Under such a state, the liquid thermal medium is heated by the electric heater 2. In more particular, a thin film form of liquid thermal medium layer 10 formed on the surface of the heater 2 is directly heated through conduction by the heater 2 making contact thereto, and thereby the liquid thermal medium is momentarily vaporized. Accordingly, the heating efficiency in this case is far more excellent than in the case of heating a liquid thermal medium while submerging a heater entirely in the liquid thermal medium, that is, in the case of heating the liquid thermal medium through conduction and convection. Therefore, there is no need to forcively overheat the heater 2, and so the liquid thermal medium would not be degraded through thermal cracking.

To the upper portion of the vessel 1 is communicated a separator tank 11 through a pipe 12, and the bottom portion of said separator tank 11 and the middle portion of the vessel 1 are communicated with each other through a return pipe 13, whose lower end 14 is located just above the heater 2. Since the separator tank 11 is separated from the vessel 1, and since the heatinsulating material for the heat-treatment apparatus, which is represented in FIG. 2 merely symbolically by a double-dot chain line frame 24, is thinner around the separator tank 11 than around the vessel 1, the temperature of the separator tank 11 is lower than that of the vessel 1, and therefore, the thermal medium vapor in the separator tank 11 is condensed and lowers in pressure, so that the vapor in the upper portion of the vessel 1 can be continuously sucked by the separator tank 11. Then the vapor passes through a choke 32 in the pipe 12, where the velocity of the vapor flow is increased and its pressured is lowered. This low pressure serves to lead impurity vapor and gas, which are apt to remain in the upper portion of the vessel 1, to the separator tank 11, and thereby prevents the temperature fall in the upper portion of the vessel 1.

As described above, the vapor within the vertically elongated sealed vessel 1 is continuously sucked into the separator tank 11, so that the rising velocity of the saturated vapor within said vessel 1 is far larger than in the case of not being sucked by the separator tank 11. Accordingly, even if the running speed of the yarns 7 is raised and thereby the heat consumption is increased, the saturated vapor can momentarily heat up the heat-exchanging wall 4 to supplement the consumed heat, and thus can maintain the temperature of the heat-exchanging wall 4 always constant.

On the other hand, the liquid thermal medium which has been condensed and liquidized in the separator tank 11 returns to the inner space of the vessel 1 through a return pipe 13. The liquid thermal medium which has entered into the vessel 1 drips onto the upper portion of the heater 2, and while it flows in a thin film form along the surface of the heater 2, it joins with the return liquid thermal medium led by the previously described guide plates 6 and is heated by the heater 2. Thus it is again converted into a vapor which fills the inner space of the vessel 1. However, a part of the impurity gas existing within the separator tank 11 by a minute amount remains in itself. Most of the remainder impurity gas consists of materials having low boiling points, and so it is hardly liquidized. Accordingly, this also remains in a gaseous state in the separator tank 11.

After the heat-treatment apparatus according to the present invention has been used for a long period of time, when the accumulated amount of the impurity gas within the separator tank 11 has been increased to such extent that any more impurity gas cannot be accommodated within the separator tank 11, it occurs that the impurity gas exists also in the upper portion of the vessel 1. As a result, the temperature in the upper portion of the vertically elongated vessel 1 would become lower than that in the remaining portion of the same. Some approaches for eliminating the uneven temperature distribution in the vertically elongated vessel caused through the above-mentioned process, are the structural features of the heat-treatment apparatus according to the present invention as fully described hereinunder. One of the approaches is the feature that one end of a purge pipe 29 is communicated with the upper portion of the separator tank 11, the other end thereof being sealed off as shown at 30, and when the impurity gas has been excessively accumulated in the separator tank 11, the sealed portion 30 is opened to extract the impurity gas to the outside and then the purge pipe 29 is again sealed off. Another approach is the structural feature that instead of providing said purge pipe 29, an evacuated reservoir tank 16 for sucking the impurity gas is connected via an extraction pipe 15 to the upper portion of the separator tank 11 and in the midway of the extraction pipe 15 is provided a needle valve 17. This needle valve 17 is adapted to be opened and closed by manipulating a knob 19 coupled to a needle 18 of said valve 17 even when the heat-treatment apparatus is in use for heating yarns 7. In addition, there is provided a bellows 21 between the needle 18 and the inner surface of a casing 20 of the needle valve 17 to perfectly seal off the interior of the separator tank 11 from the atmosphere. If said needle valve 17 is opened when the interior of the separator tank 11 has been fully filled with the impurity gas, then the impurity gas within the separator tank 11 is extracted into the evacuated reservoir tank 16 owing to the negative pressure in said reservoir tank 16. Thereafter, the needle valve 17 is closed and the heattreatment apparatus can be further used until the interior of the separator tank 1 l is again fully filled with the impurity gas.

On the other hand, the impurity gas entering into the evacuated reservoir tank 16 is cooled and partially liquidized while it is kept therein for a long period of time, and thus accumulates at the bottom as a liquid impurity material 22. During this period the pressure in the evacuated reservoir tank 16 is lowered owing to the cooling and liquidization of the impurity gas, so that when the interior of the separator tank 11 has been fully filled again with the impurity gas, it can be extracted by repeating the aforementioned operations. When these repeated operations have been conducted a number of times and the vacuum in the evacuated reservoir tank 16 has been so much degraded that the extraction has become already impossible, the lower end portion of a seal-off pipe 23 provided at the bottom of the evacuated reservoir tank 16 is cut away to suck out the liquid impurity material 22 and the impurity gas by means of a vacuum pump and to discharge the same to the outside, and after the interior of the evacuated reservoir tank 16 has been evacuated again up to a high vacuum, the lower end of the seal-off pipe 23 is sealed off to seal the evacuated reservoir tank 16. Thereafter, the heat-treatment apparatus can be used while repeating the above-described manipulations of the needle valve 17 and the associated knob 19, intil the vacuum in the evacuated reservoir tank 16 is degraded again. It is to be noted that the cooling effect for the evacuated reservoir tank 16 can be further enhanced by exposing a part of the wall of the evacuated reservoir tank 16 to the atmosphere outside of the heat-insulating material 24.

ln addition, reference numeral 25 designates a pressure-responsive switch, numeral 26 designates a bellows, and numeral 27 designates a pressure communication pipe, these jointly forming a known control device for the electric heater 2 which functions to maintain the temperature of the thermal medium vapor within the vessel 1 always constant by maintaining its pressure substantially constant.

Upon enclosing a liquid thermal medium in this heattreatment apparatus, the liquid thermal medium is injected into the vessel 1 after the interior of the same and the associated tank and pipes has been entirely evacuated up to a high vacuum and then the vessel 1 is sealed. Therefore, upon starting, the vapor pressure of the thermal medium within the vertically elongated vessel 1 is very low, because the temperature within the vertically elongated vessel 1 is the same as the temperature of the ambient atmosphere in which the vessel is placed, and accordingly, the liquid thermal medium can be readily evaporated by heating only a little with the heater 2. Furthermore, since the return liquid thermal medium condensed in contact with the inner wall surface of the vertically elongated vessel 1 is fed in a thin film form onto the heater 2 exposed above the level of the liquid thermal medium, as described above, so that the return liquid thermal medium may be evaporated before it is again accumulated at the bottom of the vessel 1, the amount of the liquid thermal medium stored at the bottom of the vessel 1 could be an extremely small amount.

In addition to the above-described first embodiment, a modified embodiment of the present invention is illustrated in FIGS. 6 to 8, in which component elements given with the same reference numerals as the component elements in FIGS. 1 to 5 is also similar in function to the latter. The difference in structure of this moditied embodiment from the first embodiment exists in that the outer surface of the heat exchanging wall 4 is shaped in a plane form, that the return liquid guide plates 6 are formed of the same material as the heatresistive and porous material provided on the outer surface of the electric heater 2, that the separator tank 11 is mounted so as to project a little above the top end of the vertically elongated sealed vessel, and that a protrusion 31 is formed in the top wall of the separator tank 11 and the top end of the extraction pipe 15 is located at the interior of said protrusion.

A further modified embodiment illustrated in FIG. 9 is different from the structure shown in FIG. 7 in that the separator tank 11 is mounted in juxtaposition to the uppermost portion of the vertically elongated sealed vessel 1 so as to position their top walls along the same plane, but it is otherwise similar to the aforementioned embodiments.

While we have described above the principle of our invention in connection with specific apparatus it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A heat-treatment apparatus for synthetic fiber yarns including a vertically elongated sealed vessel having its one side wall constructed of a heat-exchanging wall with a heating surface for said yarns formed on its outside and forming a thermal medium vapor chamber inside of said sealed vessel; comprising A. an electric heater including an upright metallic tube closed at its lower end, an electric resistance element within said tube and electrically insulated therefrom; and a cover attached to the outer surface of said tube and covering substantially the whole surface thereof, said cover being a heatresistive and mesh-type porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium, the lower end portion of the heater being submerged in said liquid thermal medium enclosed at the bottom of said vertically elongated sealed vessel with most of the remainder thereof exposed in said thermal medium vapor chamber,

B. a return liquid thermal medium guide plate attached to and disposed between the inner surface of said heat-exchanging wall and the portion of said electric heater exposed in the thermal medium vapor chamber.

C. a separator tank communicated with the upper portion of said vertically elongated sealed vessel, and

D. a return pipe having its upper end communicated with said separator tank, and having its lower end disposed within said sealed vessel at a position just above said electric heater.

2. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that a purge pipe having its one end sealed off is communicated at the other end with said separator tank.

3. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a needle valve to an evacuated reservoir tank.

4. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that between said separator tank and an evacuated reservoir tank is provided a needle valve which consists of a casing, a needle coupled to a knob, a needle valve seat formed on the inner surface of a part of said casing, and a bellows disposed between said needle and said casing.

5. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a needle valve with an evacuated reservoir tank having a seal-off pipe connected thereto.

6. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a choke with the upper portion of said vertically elongated sealed vessel.

7. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that grooves directed in the lengthwise direction for passing said yarns therethrough are formed on the outer surface of the heat-exchanging wall of said vertically elongated sealed vessel.

8. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that the outer surface of the heat-exchanging wall of said vertically elongated sealed vessel is shaped in a plane form.

9. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said return liquid thermal medium guide plate is made of a heat-resistive and porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium.

10. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is mounted to said vertically elongated sealed vessel so that the former may project above the top end of the latter.

11. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is mounted to said vertically elongated sealed vessel in juxtaposition to the uppermost portion of the latter.

12. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is formed with an upward protrusion in its top end wall. 

1. A heat-treatment apparatus for synthetic fiber yarns including a vertically elongated sealed vessel having its one side wall cOnstructed of a heat-exchanging wall with a heating surface for said yarns formed on its outside and forming a thermal medium vapor chamber inside of said sealed vessel; comprising A. an electric heater including an upright metallic tube closed at its lower end, an electric resistance element within said tube and electrically insulated therefrom; and a cover attached to the outer surface of said tube and covering substantially the whole surface thereof, said cover being a heat-resistive and mesh-type porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium, the lower end portion of the heater being submerged in said liquid thermal medium enclosed at the bottom of said vertically elongated sealed vessel with most of the remainder thereof exposed in said thermal medium vapor chamber, B. a return liquid thermal medium guide plate attached to and disposed between the inner surface of said heat-exchanging wall and the portion of said electric heater exposed in the thermal medium vapor chamber. C. a separator tank communicated with the upper portion of said vertically elongated sealed vessel, and D. a return pipe having its upper end communicated with said separator tank, and having its lower end disposed within said sealed vessel at a position just above said electric heater.
 1. A heat-treatment apparatus for synthetic fiber yarns including a vertically elongated sealed vessel having its one side wall cOnstructed of a heat-exchanging wall with a heating surface for said yarns formed on its outside and forming a thermal medium vapor chamber inside of said sealed vessel; comprising A. an electric heater including an upright metallic tube closed at its lower end, an electric resistance element within said tube and electrically insulated therefrom; and a cover attached to the outer surface of said tube and covering substantially the whole surface thereof, said cover being a heat-resistive and mesh-type porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium, the lower end portion of the heater being submerged in said liquid thermal medium enclosed at the bottom of said vertically elongated sealed vessel with most of the remainder thereof exposed in said thermal medium vapor chamber, B. a return liquid thermal medium guide plate attached to and disposed between the inner surface of said heat-exchanging wall and the portion of said electric heater exposed in the thermal medium vapor chamber. C. a separator tank communicated with the upper portion of said vertically elongated sealed vessel, and D. a return pipe having its upper end communicated with said separator tank, and having its lower end disposed within said sealed vessel at a position just above said electric heater.
 2. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that a purge pipe having its one end sealed off is communicated at the other end with said separator tank.
 2. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that a purge pipe having its one end sealed off is communicated at the other end with said separator tank.
 3. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a needle valve to an evacuated reservoir tank.
 3. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a needle valve to an evacuated reservoir tank.
 4. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that between said separator tank and an evacuated reservoir tank is provided a needle valve which consists of a casing, a needle coupled to a knob, a needle valve seat formed on the inner surface of a part of said casing, and a bellows disposed between said needle and said casing.
 4. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that between said separator tank and an evacuated reservoir tank is provided a needle valve which consists of a casing, a needle coupled to a knob, a needle valve seat formed on the inner surface of a part of said casing, and a bellows disposed between said needle and said casing.
 5. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a needle valve with an evacuated reservoir tank having a seal-off pipe connected thereto.
 5. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a needle valve with an evacuated reservoir tank having a seal-off pipe connected thereto.
 6. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a choke with the upper portion of said vertically elongated sealed vessel.
 6. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is communicated through a choke with the upper portion of said vertically elongated sealed vessel.
 7. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that grooves directed in the lengthwise direction for passing said yarns therethrough are formed on the outer surface of the heat-exchanging wall of said vertically elongated sealed vessel.
 7. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that grooves directed in the lengthwise direction for passing said yarns therethrough are formed on the outer surface of the heat-exchanging wall of said vertically elongated sealed vessel.
 8. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that the outer surface of the heat-exchanging wall of said vertically elongated sealed vessel is shaped in a plane form.
 8. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that the outer surface of the heat-exchanging wall of said vertically elongated sealed vessel is shaped in a plane form.
 9. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said return liquid thermal medium guide plate is made of a heat-resistive and porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium.
 9. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said return liquid thermal medium guide plate is made of a heat-resistive and porous material having a porosity such that capillarity may occur therein for a given liquid thermal medium.
 10. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is mounted to said vertically elongated sealed vessel so that the former may project above the top end of the latter.
 10. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is mounted to said vertically elongated sealed vessel so that the former may project above the top end of the latter.
 11. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is mounted to said vertically elongated sealed vessel in juxtaposition to the uppermost portion of the latter.
 11. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is mounted to said vertically elongated sealed vessel in juxtaposition to the uppermost portion of the latter.
 12. A heat-treatment apparatus for synthetic fiber yarns as claimed in claim 1, characterized in that said separator tank is foRmed with an upward protrusion in its top end wall. 